Purpose: The purpose of this study was to evaluate the mechanism of injury in the anterior cruciate ligament tears sustained in participation in soccer. Materials and methods: 50 patients whose knees were injured during playing soccer were enrolled in this study. The mean age was 27 years old, 47 were male and 3 female. 15 of them were either professional or amateur soccer players, the rest were non-professional. The injury mechanism was investigated by evaluation of the medical records or by telephone interview. Results: The injury mechanism involved contact injuries in 17 patients and non-contact in 33. 41 patients were bearing weight on the involved side at the time of injury, and 9 patients were not. In cases of contact injury, 9 of the 17 patients had sustained a valgus force to the knee, and 5 patients had varus force, 11 patients had their foot planted, and 6 did not. Among those patients with a planted foot, 3 patients were injured by the rotation of the thigh, 1 patient was injured by hyperextension, and there were no deceleration mechanism injuries. In non-contact injuries, 30 out of 33 patients had their foot planted at time of injury and only 3 patients did not. Of these 30 patients, 16 were injured by the rotation of thigh, 6 sustained a varus force on the knee joint and 5 had a valgus force, 5 were injured by hyperextension, and 2 by deceleration. 3 patients, who did not have their foot planted, were injured while kicking with the involved leg. Conclusions: For soccer players in this series, the most common mechanisms resulting in anterior cruciate ligament tears were non-contact, most often by rotation of the torso over a planted foot. In contact injuries, the most common mechanism was the application of valgus force by tackle.